Shredders are used for shredding (comminuting, chopping) organic pruning waste such as cuttings, branches, leaves, agricultural crops, foliage etc. and waste from landscaping or farming. Various systems are used for shredding organic matter. After shredding, the cuttings leave the shredding chamber along the discharge side.
A first known system is the disc chopper wherein a plurality of blades is mounted in the surface of a large disc, against which the organic matter is pressed when introduced into an infeed hopper, in some cases via infeed rollers, and chopped transversely between the blades and a counterblade. The chopped matter is then passed towards the back through the opening in the disc. For further discharge, vanes are used which are mounted behind the disc.
A second known system is the drum chopper, wherein a plurality of blades is mounted in the length direction of a drum wall. The organic matter is pressed against the drum wall, whereby said matter is chopped transversely between the blades and a counterblade. In this system, the chopped cuttings fall into a cavity behind the blade, wherein the cuttings are projected out of the cavity via a discharge opening under the effect of the centrifugal force created.
In the abovementioned (first) group of systems, cuttings with fixed dimensions are produced directly as soon as the organic matter comes into contact with the blades.
Such choppers have the disadvantage that they are preferably suitable for shredding branches.
In order to be able to process not only branches but also other waste, such as garden waste, flowers, leaves, agricultural crops, foliage and similar, until today a second group of systems has been used: either hammer or clapper mills wherein the organic matter is comminuted by means of clappers or hammers, or the shredder which is described in European patent EP 1 480 752, which uses an anvil and groups of blades mounted on a shaft and installed rotatably in front of the anvil.
In the second group of systems which are suitable for processing largely green waste, the discharge side of the shredding chamber is provided with a grid with passage openings for the calibration of the cuttings, known as a calibration grating. In this way, only the cuttings which have been chopped sufficiently small by the cutting means can leave the device. In this group, in contrast to the first group, the cuttings are not formed directly. The cuttings are effectively formed in two phases. First a “large” irregular piece is obtained, which is then comminuted to the desired size in the shredding chamber. The calibration grating determines how long the cuttings remain in the shredding chamber. The disadvantage of this system however is that once the cuttings leave the shredder, they fall directly onto the underlying ground under the effect of gravity, whereupon they must then be collected in order to be disposed of. A possible solution to this problem is the placing of a catchment container (sack) of flexible material on the discharge side of the shredding chamber. The fixing of such a sack is however awkward, and in addition the attached container (sack) must then be emptied regularly.
To facilitate the discharge of shredded matter, WO 2007/086040, EP 2 452 791 and DE 36 31 337 describe a number of systems, wherein a suction is created by a fan element which rotates in a separate housing, and wherein displacement means are provided for moving the shredded matter to the centre of the fan element because the suction is strongest there. These systems are often complex. In addition, clogging often occurs because the shredded matter is only discharged under the suction effect created by the fan element. Thus only a limited passage opening is present for the shredded matter, because too large a passage opening would have a negative effect on the pressure build-up.